...drive in the rain to keep the dust down?
The rain was what clued me in. I got caught out in a light shower and when it was over, I pulled off and toweled the screen dry. The front was pretty clear as the water had been blown off. The inside was really covered! This all came from the front following the transmission tunnel then into the car. Those gaps are huge!...
Not sure I've noticed it the same. 4 days hard driving in Spain over the Summer (heat, rain, ...) meant that yes, the chamois leather picked up some grime from the inside windscreen when cleaning the dew off in the morning... but nothing special! Perhaps my big feet block the gaps on mine
